Marine platforms



R. O. MARSH, JR

MARINE PLATFORMS a Sheets-Sheet 1 INVENTOR. RICHARD. O. Mes/1 die.

31' wwwamanwum.

A TTO/FNEYS.

Oct. 13, 1959 Filed July 23. 1954 use v R. b. MARSH, JR

MARINE PLATFORMS Filed July 23. 1954 3 Sheets-Sheet 2 I I I I -M T I I II I m m I I. H WI l I WQ II I .1. IIP LFII I I LIWI IIIIIIIIIIIIII WR/cr/A RD QMA RSH JP.

ATTORNEYS.

0a; 13, 1959 R. o, MARSH, J 2,908,141

MARINE PLATFORMS 5 Sheets-Sheet 3 1 Filed July 23. 1954 INVENTOR-RICHAEDOMQESHJE. v

. v BY A TTORNE'VS'.

2,908,141 r MARINE PLATFORMS.

Richard 0. Marsh, Jr.,-Baltimore, Md., assignor to RaymondiInternational.Inc., New York, N.Y., a corporation .of New Jersey 1 Application July23,1954, Serial No. 445,303

'2 Claims. (Cl. 61.46.5)

invention relates to mobile -marine platforms of types which can beanchored in any desired off-shore location,-and more particularly itrelates to such platforms which are designed for use in ocean depths ofconsiderable magnitude.

Mobile marine platforms of various constructions are well knownbutcertain. disadvantages however have been manifested in their actualoperation. These types of platforms find utility in many fields .but aremostadvantageous in .oflf-shore oil well drilling operations In order.to meet the requirements of a successful off-shore oil welldrillingoperation it is a primary requisite that the plat-- form used bestable regardless of thecondition .of the sea in which it is anchored.In effort to provide this necessary-stability the platforms heretoforeknown have in many instances employed rigidsupporting studs or columnarstructures which extend downwardly from the platform to the anchor meanspositioned on the sea bot tom. While such constructions, are quitesatisfactory for shallow water operations, it obvious that, when theocean depths at the desired location range intothe hundreds of feet,such rigid members must necessarily be ofsuch magnitude as to becumbersome, unwieldy and too costly. Since the platform, to be useful,must be self-contained as well as mobile, .the problem of transportingsuch huge rigid supporting structure becomes a practical impossibilitywhen'substantial ocean depth's are involved. forms in depths beyond 100feet for example, experience has indicated that cables or similarflexible anchor lines, that .can be conveniently stored on deck when theplatform is being. towed, should be used to. interconnect the j Workingplatform. with its 7 anchorage base. Although yarious platformconstructions have been proposed which do employ such flexibleanchor'lines they have failed to satisfy the requirements of providing astable working 7 platform while maintaininga construction which issimple "enough-to avoidcontinual operational difiiculties orbreakdowns'ff-It is of course-obvious that the problem of maintainingstability assumes greatly increased proportions when flexible cable orchain means, ratherthan rigid supports and the like, are usedto-intercon-nect the Cplatform with its anchorl Any such flexible anchorlines must: be. maintained uniformly under tension the platformis to.resist pitching and tossing under the normal wage action 'andsince thetendency of any floating body is-alternately to rise on the crest andthen fall in the troughof; such waves, thereby-alternatelycausing strain.andnsla ck -in cables, the problemof maintaining uniform tension .is;a.difilcult one .Moreoverwhen flexible anchor liuesanetutil-izedztheproblem aoftavoiding tang-ling or snarling. thereof with resultantoperational breakdowns is 2. 1 involves the dangerof tangled anchorlines. Moreover in order to provide a suitably broad and stableanchorage base, it would be desirable to have such anchor lines extenddownwardly and outwardly at an angle from the platform ,rather thanmerely vertically. downwardly. With a plurality of individual anchorssuch an anchorage base is diflicult to maintain since the naturaltendency of those anchors will be to shift or creep inWaId1y* tO.a

position beneath the platform; Any such movement of 'cloursenot onlydestroys "the-broad anchorage base but also, causes the anchor lines tobecome slack thereby destroying the stability ofthe platform. When it isrealized that-sornetinies the ocean depths involved mayrange up tohundreds of feet, the dimensions of such problems take on more seriousproportions.

These and other disadvantages of the constructions I heretofore knownare overcome by the present invention whichprovide's'a mobile marineplatform relatively simple 'in construction and in its principles ofoperation, and designed moreover to provide a working deckspace which isstable under all the, usual conditions of the surrounding sea, andfurthermore capable-of operation in ocean depths of the orderof 100 to600 feet; The platform ,of the invention comprises a unitary floatmembercarrying an elevated deck structureand a unitary anchor member connectedto saidv float member by. flexible anchor cables or chains. -Bothmembers are buoyant and have hollow chambers which are provided. withsuitable conduit connections designedto permit the entry and removal ofWater as desired in order that their buoyancy can be adjustablycontrolledJ The horizontal dimensions of the anchor bodyareconsiderablygreater than those ofthe float body so as to providev abroad based anchorage meansand said anchor body is-preferably providedwith an open central portion of a size'sufficient to encompass the floatfbody; Thus in the mobile condition of the platform both members mayfloat on the-surface of-the water with'the float member positionedwithin the central open- In order to successfully operate such plat--ing of the anchor member. Furthermore .it is preferable according -.tothe invention that the float and anchor members be so proportionedrelative to. one another that the net. buoyancy of the float memberbegreat-enough to support the weight of the anchor body when the'latter iscompletely flooded :with water.

Preferably the anchor memberis in the formof a large hollow sheet metalring-which maybe ofcircu-lar cross-section; However, thew-ring may berectang-ular, square or polygonalcross-section. Also, the float memf bermay preferably be in the form of a hollow, sheet sponding .to-the shapeof the anchor member. I

In operation, the platform is towed to the desired.- olffrneta'lringeither circular or 'othershape preferably correshore location and theanchor member is then flooded with water thereby causing the same tosubmerge until it finally comes to a position of rest o-nithe seabottom.

During this descent ofthe anchor body, the anchor cables, which run fromwinches provided on the elevated deck through suitable guide means onthefloat member to the anchor member, are' of courseslacked off. Withtheanchor member in this position,thefloat member and its elevated-deck arein effect tied to the ocean floor; but, since such float member is stillfree to rise and falliin' the I trough of surfacewaves, stability islacking. To provide ofjcoursel ofdistinct, importance. 'Heretoforeproposed j as a consequence of any severe strain being applied, to thecaus or cables running to that particular anchor. This thisflessentialstability the floatrnember'is partially flooded with water so. as todecrease its buoyancy toanamount which is insufficient to supporttheweight of the anchor member. "Tension is then applied to the cablesby taking upon therwinches, and the float member is thereby pulleddownuntil it is totally'submerged below thewa'ter surface a'ta leyelwhich is'below the trough 'of the largest 1 contemplated waves. ,Due, tothe continuous,., upward buoyant force upon the float member" in thisposition,

' Fig. 1 isan elevatl iform of the invention anchored in operatingposition.

- anchormembers, and Fig. 7 is a view similar to Fig. 6 but showing analter- ;native embodiment. V

I Referring now in further detail to the drawings and j member.

and therefore the working deck space will be maintained stable. And ifthis working deck space is origlnally constructed at. a suflicientheight above the float vmember,

itjcan'be maintained at a level which is above the crest :Ofthe, highestcontemplated waves even when the float jrnember is ,thus submerged. Whenit is desired to move I the platform to a new sea location the water ispumped font of theinterior of the float member thereby increasing .thebuoyant force exerted by said member to its original amount which byinitial design is greater than the weight .of the anchor body. Once thishas been accomplished the float member will lift the anchor member fromthe sea bottom and will itself return to the water surface.

Then by. taking up on the winches, the anchor body can beraisedfurther,and when it nears the surface of the water by pumping out its hollowinterior, it can be floated the remaining distance to the surface. Theplatform is then in position for movement to the next off-shore drillinglocation.

. Other and more specific objects, features and advan-- tages of theinvention will appear from the detailed description given below, takenin connection with the accompanying drawings which form a part of thisspecification and illustrate by way of example the present preferredembodiment of the invention.

In thedrawings:

onal view showing the mobile plat- Fig. 2 is a schematic elevationalview showing the platform in mobile condition with both float and anchormembers at the Water surface. Fig. 3 is a somewhat schematic elevationalview, showingthe platform with the parts thereof in the positions 'assumed after the anchormember has been submerged.

' the anchor cables will be continuously held under tension the likelinkages as well as wire or other forms of rope or cables. This workingdeck is supported from the float member 21 by rigid tubular orfabricated supporting columns 27 which rise from said float member andmaintain the deck 26 at a fixed elevation thereabove. In constructingthe platform the dimensions of these supports 27 and the consequentelevation of the deck 26 are calculated, having in mind the size ofthewaves which are to be encountered by the platform at its off-shoredrilling location. As will be more fully described'hereinafter it isnecessary'that the deck 26 be constructed at a sufficient elevationabove float member 21 so that when said member is submerged to a levelbeneath the trough of the largest wave, the deck is at the same timepositioned at a level above the crest of the highest wave.

An oil well derrick 28 of common construction is mounted on deck 26 andis of course designed to sink the customary type oil' well casing 29down throughthe open central portion of the float and the anchor membersinto the sea bottom 30. Similarly mounted on the working deck 26 areconventional pumps 31 which are designed to be connected via suitablehose means 38, 39 and'42, .43

(Fig. 7) and fluid port means 40, 41 and 44, 45, with the interiors ofthe anchor and float members respectively when it is desiredto'introduce or remove water from either of these members. i I

Referring now to Fig. 6 one means of rigging the anchor cables 23 isthere shown. Each cable 23 is secured at its lower end to an eye 32provided on the outer surface of the anchor member. The other end of thecableis led through a hollow conduit 33 which is welded in position inthe interior of the float member 21 extending from the bottom to the topthereof with said float member being suitably bored at 34 and 35 inalignment with said conduit so as to permit passage of the cable.Tubular supports 27 are welded or otherwise secured to the exterior ofthe float member in alignment with conduits 33. These tubular supportsare similarly hollow and the cables 23 pass .therethrough and are led tothe deck winches 25. In the alternate embodiment shown in Fig. 7 eachcable 23 is secured to an eye 36 provided on V the exterior of theanchor member and extends therefrom particularly to Fig.1 there is showna mobile marine 1 platform 20 which comprises a ring-shaped, water tight'floatfme'mber 21 and a similarly ring-shaped water tight anchor'rnember22. Both of these members are preferably fabricated from steel or othersuitable sturdy structural material such as is capable of withstandingthe enormous stresses to which a device of this type must be subjected.It should be understood that while these members are preferablyring-shaped as shown, they may also f assume various other shapes suchas a rectangular frame-.

'like'strubtur. It is preferred however that the anchor member besubstantially largerrthan the float member and be provided with an opencentral portion 22' which is large enough to receive said float member.When ring- 'shaped,the anchor member preferably has a diameterapproximately twice that of the diameter of the float Thus when thistype of platform is to be used in oceandepths ranging from 100 to 600feet the float member can for-example have adiameter of approximately200 feet and theanchor member a diameter of approximately 400 feet.Interconnecting these two members are a plurality of an'chor cables orchains 23 which i are secured at one end to the anchor member and extendtherefrom to or through suitable guide means 24 provided on the float.member and thence upward to winch and pulley means 25 positioned on aworking deck 26.

The cables are preferably, although not necessarily, arranged incrisscrossed relation as shown. The. word eablesflasaused herein,isintended to include chains or to a pulley guide 37 mounted on theexternal surface of the. float'member 21, and through the pulley guideto the deck winches. a r

Referring now to Figs. 2 to 5 the operation of the vdevice will bedescribed:

Fig. 2 portrays the platform 20in the mobile condition ready to 'betowed to the desired off-shore drilling location. As shown both theanchor and float members 21, 22 arefloating at the surface of thewaterwith the floatmember 21 positioned within the open central portion 22'of the anchor member. Whenthe platformhas been towed to the desireddrilling location, water is introduced into the interior of the anchormember so as to flood the same and thereby cause it to submergeto theposition shown in Fig. 3, resting on the bottom of the i seal Variousmeans for flooding this anchor member may be used, but for purposes ofillustration a Water hose 38 and an air hose 39 may be connected asshown in Fig. 7 and water pumped into the interior of the anchor member22 through hose 38 by the pump 31 while air is permitted to evacuatethrough hose 39. Suitable means may if desired be provided forpermitting disconnection of these 'hoses prior to the completesubmerging and downward descent of the anchor member. As the anchormember descends to its position of'rest on the sea bottom 30 as shownxinFig. *3, the winches 25 are released so as to slack off anchor cables 23thereby permitting the float member 21 to remain on the surface. In thisposition the float member. and its elevated, deck structure will i ofcoursebe in eifect tied to the desired off-shore drilling location.However due to the flexibility of cables 23 he 1 st .1 udi t k Ev fqqure r e an ta Fwithmny surfacewavesmhich may :be present in thepariticular area.

To eliminate thisundesirable motion and to render the .platformsubstantially stable, ;the interiorof the float I :member 21 ispartiallyflooded with water, as shown e :the floatrmember toapositionwhere the same is held at :a 1etve'lwhich1is .belowthe .troughof thelargest waves -.-.contemplated in thevparticular area, it is possible to.cre- -ate arelationship of the-parts .of the platform structurewhereinthe cables .23 areecontinuously held under ten- .sionidueetothecontinuous upwardthrust caused bythe .ibuoyant .force'acting .onthefloat-member 21. In this :positionzthe float member will .remainsubstantially stationaryrandthe elevated deck structure 26 willof coursepresent a most stable working area; As mentioned above .the initialdesign of this deck 26 it is of course im- :portant to build the same atsuflicient elevation .above the "floatlmernber 21 .so that, when thelatter is held in his submerged position, the deck itself will still .bemaintained .at a level which .is sufficiently raised above the crest ofthelargestcontemplated waves.

. It .will be observed that .sincethe anchor member has .a..diameterwhich is substantially larger than the diameter of the float member, theanchor cables descend downwardly and outwardly from the float memberthereby providing a broad, and stable anchorage base.

In a yp cal case, for example, where the anchor ring has a diameter of400 feet and a cross-sectional diameter =95, IZQJ e L i t ismadaef linch-st el p a s we tw uc i fn i hh heod .Qf.. ons which if d r mi tbiuaeassslsay 2000 to 25 tons y addi .ean tete tatt a e qrthereqt- In ucha e e flo ring member 2 may have adiameter, of about 200 feet and across-sectional diameter of 20 'feet giving a norbuoyancy. when. empty.of. approximately 6000 tons.

The weight of such a float ring plus the weight of the deck, decksupports and drilling equipment would amount to about 800 tons and thenecessary cables another 80 tons thereby leaving a net buoyancy of about5120 tons. When the anchor member has been submerged, this net buoyancyof the float member can be reduced to 1000 tons by partially floodingthe same with 4120 tons of water or other ballast. Then by taking up onthe winches the float member can be submerged, and when submerged thebuoyant force acting thereon will create a total tension in the cablesof about 1000 tons, ample to retain the platform structure insubstantially stable condition in the presence of quite heavy seas butinsuflicient to raise or dislodge the anchor ring which has a weight of1500 tons. A platform of this description is particularly suitable foroff-shore oil drilling.

Similar but smaller arrangements may be used for other purposes, such assoil test boring rigs, etc. and then the overall diameter of the anchorring may, for example, be 50 feet with a cross-sectional diameter offeet. Such an anchor member if made, for example, of %1 inch steel platewould weight about 75 tons, which could be increased to 100 tons byadding concrete or the like. In this case the float ring 21 might havean overall diameter of 25 feet and a cross-sectional diameter of 10 feetto provide a buoyancy of about 180 tons. Assumin that this float ringwere constructed of /8 inch steel plate, it would weigh approximately 18tons, which together with about 10 tons of deck structure, 2 tons ofcables and .other while the cables assume angular positions.

'7 'tons of boring equipment would' bring the total weight to about 37tons leaving a net buoyancy'of 143 tons for the float member. Bypartially'flooding the same with 93 tons of water ballast, this buoyancycanbe reduced to 50 tons, thereby permitting the float unit to besubmerged and create a 50 ton-tension in the anchor cables, which wouldbe adequate to hold the platform stable but would be insufficient tolift the 75 'ton anchor'ring.

In view of the above factors the advantages of th'e present inventionmay now be better appreciated as compared to prior proposals involvingpluralities o'f anchoring cables each connected to individual anchors."If such individual anchors are placed directly below the platform,then, depending upon wind and wave conditions, the platform will tend'tomove to one side Or an- But any such sideways movements of the platform"will of course necessitate suspension of the drilling operation. On'theother hand, if, to prevent such sideways move- .ment of the platform,the individual anchors are dropped in positions laterally outward of theplatform so that the cables therefrom are inclined inwardly'in var-iousdirections and upwardly to the platform, the following difiicultywilloccur. If the water conditions are such *astend to cause the platform totravel in one direction, thenthe holding tension will be largelyconfined to the cables which extend down to the anchors positionedin-the opposite direction, andthe remaining cables will become slack orhave very little tension. Thus the'holding action will be confined to afew individual anchors-and those'will tend to be dragged along the oceanbottom inwardl'yof the assembly, thereby allowing the platform to shiftits position and eventually perhaps allowing all the cables to becomeloosened and entangled and allowing the submerged float means to rise uptoward the surface of the sea.

With the present invention however using a unitary heavy, singleanchorage, particularly if in the form of "a ring larger than the floatmember, there will be no possibility of one part of the anchoragecreeping along the ocean surface with respect to-other parts andaccordingly all of the cables will retain their uniform tension and thushold the platform submerged to the desired degree and at the desiredlocation. i I

"location the winches '25 will be freed so'as to release the tension oncables 23 thereby permitting the float member 21 to rise to the surfaceof the water under the action of the buoyant force thereupon. When thismember reaches the surface, as shown in Fig. 5, water hose 42 and airhose 43 are connected and the water pumped out of the interior of thefloat member by means of pumps 31. This action of course restores tothat float member its original buoyancy which by design, is in excess ofthe weight of the anchor member 22. Therefore by then taking up on thewinches 25 and thus applying tension to the cables 23, the anchor membermay be raised from the bottom of the sea to an intermediate positionsuch as is shown in dotted lines in Fig. 5 or at a position nearer thewater surface. When this position of the anchor member is reached waterhose 38 and air hose 39 are then connected to that member and the waterpumped out from the interior thereof, thereby restoring its buoyancy andpermitting the anchor member to rise to the surface of the water andreturn to its initial position as shown in Fig. 2.

Various means may be provided by which these hoses 38 and 39 areattached to the anchor member when the, latter is in an intermediateposition preferably near the water surface. This can be accomplishedbydivers or other expedients if necessary. Depending upon the depths ofthe water in which the platform is to be anchored the precise mechanismfor elevating the anchor member may of course vary. Thus as describedabove in con- A7 :nection with, Fig. 6, a simple rig has been shownwhich may be used'with success in relatively shallow depths. Howeverwhen the depths involved range towards the '500:foot mark, 'the'rigshown in Fig. 7 may be preferred, since the pulley guide 37 on theexterior of the float member provides a better angle of lift whichpermits the 'anchor'member to be pulled up a greater distance from thesea bottom thereby decreasing thedepth to which e diver or othermeans'must descend in order to attach -water hose 38 and air hose 39.

The'invention, in addition 'to being useful for offshort oil drillingpurposes, may be used for providing either mobile or permanent bridgepiers, docks and airplane runways over deep waters. I

"Although certain particular embodiments of the invention are hereindisclosed for purposes of explanation, 'various further modificationsthereof, after study of this ,specificatiomwill be apparent to thoseskilled in the art to which the invention pertains. 'Reference shouldaccordingly be had to the appended claims in determining.

;the scope of the invention. What is claimed and desired to be securedby Letters Patent,'is:

1. A mobile marine platform comprising a buoyant, generally ring-shapedfloat member carrying a working deck structure supported at a levelthereabove, a univtary, generally ring-shaped, normally buoyant anchormember having an open central portion of a size sufli cient to encompassthe float member, said float and anchor members resting on the watersurface with the float member nesting within the open central portion ofthe anchor member when the platform is in the mobile condition, aplurality of anchor cables interconnecting extend downwardly andoutwardly from the float member to the anchor member, said float memberhaving an original buoyancy greater than the weight of said anchormember when the latter is flooded, means for controlling the buoyancy ofthe float member by flooding or deflooding samewhereby its buoyancy maybe decreased by partially flooding the same until the net buoytheanchormember, andmeans for taking iup on said cables'whereby said float membercan be pulled down to a level beneath the trough ofthe waves with thedeck remaining above the wave crests the cables thereby held underuniform tension sufficient 'to maintain the deck substantiallylstable.2. A mobile platform comprisinga buoyant float member having an elevateddeck supported thereabove,'"a unitary anchor member that is normallybuoyant and has a periphery greater than that of said float member andanopen central portion of a'size sufiicient to receive the float member,said float and anchor members floating on the water surface with thefloat member positioned within the open central portion of the anchormember when the platform is in the mobile condition, said anchor memberbeing adapted to be flooded with water and to sink to the sea bottomwhen the platform is in the operative position, a plurality of anchorcables extending from said float member downwardly and out- -wardly tosaid anchor member, meansprovided'on the deck and connected with saidcables for taking up or slacking oif 'on the cables, and means forflooding and deflooding the float member operable to decrease itsbuoyant force to a value less than the weight of the flooded anchormember whereby said float member can be the elevated deck substantiallystable, said float member havinga maximum effective buoyancy whendeflooded great enough to support the weight of the flooded anchor'member whereby the latter may be raised from the sea bottom by means ofthe cables so that the platform may be moved to a new location.

'R eferences Cited the file of this patent T 3 UNITED STATES PATENTSGreat .Britain j Oct. 29;

"1,291,034 I Lindquist Jan. 14, 1919 2,399,611 Armstrong May 7, 19462,476,309 Lang July 19, 1949 2,534,480 Shannon Dec. 19, 1950 1 FOREIGNPATENTS V Y

